(a) Technical Field
The present disclosure relates, in general, to a separator for a fuel cell. More particularly, in preferred embodiments, the present invention relates to a separator for a fuel cell, in which a strength reinforcing means is integrally formed in a region, and further is not supported by a gasket, over the region from manifolds, through which reactant gases and coolant are suitably supplied, to a reaction flow field, in which a reaction takes place, thus suitably preventing local deformation of the separator.
(b) Background Art
A typical structure of a fuel cell stack will be described briefly with respect to exemplary FIG. 8. Preferably, a membrane electrode assembly (MEA) is located in the middle of the fuel cell stack and includes a polymer electrolyte membrane 10, through which hydrogen ions (protons) are transported, and an electrode/catalyst layer such as an air electrode (cathode) 12 and a fuel electrode (anode) 14, in which an electrochemical reaction between hydrogen and oxygen takes place, suitably disposed on each of both sides of the polymer electrolyte membrane 10.
Preferably, a gas diffusion layer (GDL) 16 and a gasket 18 are sequentially stacked on both sides of the MEA, where the cathode 12 and the anode 14 are located. A separator 20 including flow fields for supplying fuel and discharging water generated by the reaction is located on the outside of the GDL 16, and an end plate 30 for supporting and fixing the above-described components is suitably connected to each of both ends thereof.
Accordingly, at the anode 14 of the fuel cell stack, hydrogen is dissociated into hydrogen ions (protons, H+) and electrons (e−) by an oxidation reaction of hydrogen. Preferably, the hydrogen ions and electrons are transmitted to the cathode 12 through the electrolyte membrane 10 and the separator 20, respectively. At the cathode 12, water is suitably produced by an electrochemical reaction in which the hydrogen ions and electrons transmitted from the anode 14 and the oxygen in air participate and, at the same time, electrical energy is suitably produced by the flow of electrons.
The structure of a conventional separator formed of a thin metal plate is described herein.
FIG. 6 is a cross-sectional view taken along the width of an exemplary conventional separator, and FIG. 7 is a cross-sectional view taken along the length of the conventional separator.
A metal separator formed of a thin metal plate having a thickness of 0.1 to 0.2 mm by a molding process such as stamping to have flow fields can considerably reduce the manufacturing time and cost compared to a graphite separator formed by a mechanical process.
Preferably, a pair of first separators 100a are suitably stacked on one side of a membrane electrode assembly (MEA) 400 including an electrolyte membrane and a pair of second separators 100b are suitably stacked on the other side of the MEA 400, thus forming a unit cell. Preferably, a plurality of such unit cells are suitably stacked and an end plate is suitably connected to each of both ends thereof, thus forming a fuel cell stack.
The first and second separators 100a and 100b form reaction flow fields 104a such as an anode flow field through which hydrogen flows and a cathode flow field through which air flows.
The reaction flow field 104a (anode flow field or cathode flow field) is suitably formed between the bottom side of the first separator 100a and the top side of the MEA 400, the reaction flow field 104a (anode flow field or cathode flow field) is also formed between the top side of the second separator 100b and the bottom side of the MEA 400, and a coolant flow field 104b is suitably formed in a space between the pair of first separators 100a and in a space between the pair of second separators 100b. 
Preferably, a gasket 300, which serves to suitably prevent reactant gases from leaking to the outside and to support the stacked separators, is suitably inserted and fixed to the corners of manifolds, through which the reactant gases are suitably supplied to and discharged from the respective reaction flow fields of the first and second separators 100a and 100b, and the outer circumferences of the first and second separators 100a and 100b. 
Preferably, the separator 100 integrally formed with the gasket 300 may be divided into a reactant gas and coolant entrance region 102, a flow diffusion region 106, and a reaction flow field region 104 with respect to the flow path of the reactant gases.
Hydrogen, air, and coolant manifolds 112, 114, and 116 each having a rectangular hole shape and suitably formed on both ends of the separator 100 are preferably provided in the reactant gas and coolant entrance region 102. The gasket 300 is suitably attached to both sides of each of the manifolds 112, 114, and 116 to maintain airtightness of the reactant gases and suitably support the stacked separators.
Accordingly, fluids flow from the reactant gas and coolant entrance region 102 to the reaction flow field region 104 through the flow diffusion region 106, in which no support such as the gasket is provided. Therefore, local deformation easily occurs in this region by a pressure difference between the reactant gases and the coolant during operation of the fuel cell.
The reaction for generating electricity takes place in the reaction flow field region 104, in which the anode flow field, the cathode flow field, and the coolant flow field are suitably formed. Since the respective flow fields have concave-convex portions, in which concave and convex shapes are repeated along the width of the flow fields, the concave-convex portions that form the respective flow fields suitably support the stacked separators.
Preferably, in the conventional separator having the above-described structure, while the reactant gas and coolant entrance region and the reaction flow field region are suitably supported by the gasket or the concave-convex portions, the flow diffusion region is not suitably supported by any means. Therefore, there are problems in that local deformation may occur due to the pressure difference between the reactant gases and the coolant during operation of the fuel cell to suitably reduce the surface pressure of the adjacent gasket, which causes the gasket to get loose, thus suitably deteriorating the airtight performance of the gasket.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.